Patent GB-568690-A (GB)
Title: Improvements relating to braking systems
IPC: B60T13/68
Filed: 1943-01-01
Abstract: 568,690. Hydraulic brakes. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Jan. 1, 1943, No. 35. Convention-date, Jan. 6, 1942. [Class 103 (i)] A hydraulic brake system for a train of railway vehicles comprises on each vehicle, a pump circuit through which liquid normally flows and an electrically controlled valve device adapted to restrict the flow and thus to build up pressure in a brake cylinder to a value dependent upon the current strength determined by a driver's switch. The brakes are also applied upon the opening of a second circuit by a deadman switch, by conductor's switches, by a switch operated by a ramp on the track and by the breaking of a vehicle coupling. The system shown comprises on each vehicle a valve device 1 provided with passages 23, 33 to which the inlet and outlet pipes 12, 11 of a pump 2 are respectively connected, a brake cylinder 9 being also connected by pipe 13 to the passage 33. Operation is effected by a solenoid 15 having two coils 81, 82 which are normally energized and de-energized respectively so that a lever 16 is held in the position shown against the action of a spring 83, and holds open a valve 34 by engagement with a pin 29 on a diaphragm 21. Liquid thus normally circulates from the pump through pipe 11, passage 33, valve 34, passage 23 and pipe 12. When the coil 81 is de-energized for emergency operation, the lever 16 moves to a mid-position, the valve 34 closes and pressure builds up in passage 33, pipe 13 and brake cylinder 9 to apply the brakes, the pressure being limited by a spring-pressed relief-valve 71 disposed in a byepass between the passages 23, 33. A further connection between the passages 33, 23, through passages 49, 42 is normally closed by a valve 52 carried by a diaphragm 47 and which seats at 56. When, for service operation of the brakes by the driver's pedal 91, the coil 82 is energized simultaneously with de-energization of the coil 81, the lever 16 is moved sufficiently to the right to engage a pin 46 carried by a diaphragm 38 and thus to unseat the valve 52, and to close a passage 59 through the valve body by engagement with a slidable valve 61. The valves 34, 61 being closed, the pressure builds up in the passages 33, 49, chamber 48 and the brake cylinder 9 until, acting on the diaphragm 47, it is just sufficient to overcome the force exerted by the solenoid on the lever 16. The parts then return until the valve 61 is unseated to an extent such as to maintain a pressure in the chamber 48 and the brake cylinder corresponding to the current strength in the coil 82. The coils 81 are connected to the return train wire 87 and to the train wire 86 joined to the train wire 85 which includes the normally closed conductor's switches 5 and a switch 4 arranged to be opened by a track ramp 117. The wire 85 is normally connected through a pair of spring-urged contacts 95, 94, contact 93 on the pedal 91, wire 96, a deadman switch 6 and wire 98 to the battery 10. The coils 81 are thus normally energized and are de-energized to apply the brakes as above described, when any of the switches 4, 5, 6 are opened or in the event of breakage of the wires 85, 86 as by the breaking of a coupling. The coils 82 are connected to the return train wire 87 and to the train wire 88 which is connected to a rheostat 102 the pedal-operated contact arm 108 of which is connected to the battery 10 by wire 109. Operation of the pedal 91 to effect a service application of the brakes disengages the contacts 93, 94, 95 to de-energize the coils 81 and at the same time engages the contacts 107, 103 of the rheostat 102 thus energizing the coils 82 to a degree dependent upon the movement of the pedal. As above described, the braking pressure is dependent upon the strength of the current established in the coils 82.